The invention relates to a method for positioning the slitters of a slitter-winder in a paper or board machine, in which method the slitters of the slitter-winder are placed in position in slitting to slit component webs to the desired width, in which method the slitters are moved to a new slitting position as a normal movement when the slitter-winder has stopped after slitting according to the preceding slitter setting.
With respect to the prior art, reference is made to FI patent 68 185, which describes a method for determining the position of a movable device or a member of this device and/or for determining a corrective movement to be performed from this position by means of a movable measuring device that observes and records the position. This publication describes the use of the method, for example, in a system used in longitudinal slitting of a paper web, in which system the movable device is a slitting device and the measuring device is in a position arrangement which comprises actuating members for controlling and performing the movement of the measuring device in the cross direction of the web.
As known in the prior art, the slitter-winder comprises slitters which are placed side by side in the cross direction of the web and by which the web is cut into several component webs. The width of component webs and, thus, the position of a slitter or slitters can be very different on different slitter settings depending on the desired widths of the rolls to be produced. The slitters must be placed, in a manner corresponding to the desired roll widths, in a correct slitting position in the width direction of the web.
In the slitter-winder, the movements of the slitters are made, as known in the prior art, when the last set of the preceding slitter setting has been discharged and the slitter-winder has stopped. In the arrangements known in the prior art, the time of movement of the slitters is one minute on average. In one application known in the prior art, the apparatus moving the slitters comprises only one actuator for movement, which is common to all slitters. The actuator is an electric servomotor which moves the slitters by means of a ball screw and transfer rods. By this means, the transfer motors provided for each individual slitter known in prior art applications have been avoided. The stroke length of the transfer rods is about 1 m and, when the stroke has reached the end limit, the direction of movement must be changed. All the same slitters moving in the same direction must move at the same pace, slitters are being moved only in one direction at a time. Sometimes it is necessary to move mere transfer rods backwards without slitters if their remaining stroke is not sufficient for the movement distances of all slitters.
As known in the prior art, in the settings of the slitter-winder the number of rolls to be produced is generally smaller than the maximum number of rolls, which means that one or more slitters are not in use, i.e. they do not cut the web. In most cases, however, these slitters cannot remain unmoved, because otherwise they might obstruct the movement of the slitters which will be used.
As known in the prior art, the slitter movement sequence performs several strokes of transfer rods in both directions until all slitters are in position, and the movements are continued in the same direction as long as there remain any slitters to be moved or until transfer rods are at the end limit. In that case, the direction must be changed and the sequence is continued. It may be necessary to continue with these partial movement sequences in both directions several times if the stroke length of the transfer rods is not sufficient to position the slitters which must be moved the very longest distance. Every time the transfer rods move, all the slitters to be moved in the same direction participate in the movement and the slitter making the shortest movement is left in position first. Thus, the total movement time is not merely the time of movement of the slitter to be moved the longest distance at a constant speed because this slitter must stop when each of the other slitters is placed in position.